The invention relates to inductive charging of a rechargeable battery in a vehicle. In particular, the invention relates to a method and a corresponding apparatus for positioning a vehicle over a primary coil for inductively charging the rechargeable battery of the vehicle.
Vehicles, particularly vehicles with electric drive, include rechargeable batteries for storing electric power. The rechargeable battery of a vehicle can be charged by connecting it to a vehicle-external power source (e.g. by connecting it to a public power grid), for example. One approach for automatically, wirelessly, inductively charging the battery of the vehicle involves the electric power being transmitted to the battery from the ground to the underbody of the vehicle by way of magnetic induction across the free space under the body. This is shown by way of example in FIG. 1a. In particular, FIG. 1a shows a vehicle 100 having a store 103 for electric power (e.g. having a rechargeable battery 103). The vehicle 100 includes what is known as a secondary coil 102 in the vehicle underbody, the secondary coil 102 being connected to the store 103 by way of impedance matching—not shown—and a rectifier 101.
The secondary coil 102 can be positioned above a primary coil 111, the primary coil 111 being placed on the ground in a garage, for example. The primary coil 111 is connected to a power supply 110. The power supply 110 can be a radiofrequency generator that produces an AC (alternating current) current in the primary coil 111, as a result of which a magnetic field is induced. When there is sufficient magnetic coupling between the primary coil 111 and the secondary coil 102 across the free space 120 under the body, the magnetic field induces a corresponding current in the secondary coil 102. The induced current in the secondary coil 102 is rectified by the rectifier 101 and stored in the store 103 (e.g. in the battery). In this way, electric power can be transmitted wirelessly from the power supply 110 to the energy store 103 of the vehicle 100.
In order to achieve sufficient magnetic coupling between the primary coil 111 and the secondary coil 102, the secondary coil 102 of the vehicle 100 should be positioned above the primary coil 111 (which is also referred to as ground unit) with a certain precision (typically ±10 cm). The present document describes a method and an apparatus that assist a driver of the vehicle 100 in positioning the secondary coil 102 above the primary coil 111. Assistance in positioning is important particularly because the driver cannot see the ground unit 111 in the last phase of positioning the vehicle 100 because the ground unit 111 is then situated under the vehicle 100.
According to one aspect, a control unit for a vehicle is described. The vehicle may be particularly a two-track vehicle, such as a motor car, a road vehicle and/or an automobile. The vehicle includes a secondary coil for picking up electric power from a vehicle-external primary coil. Typically, the secondary coil is attached to an underbody of the vehicle. The vehicle-external primary coil is placed on the ground in a parking space for the vehicle, for example. The primary coil and the secondary coil form a transformer when there is magnetic coupling between the primary coil and the secondary coil. In order to ensure sufficient transmission of electric power from the primary coil to the secondary coil, the distance between the secondary coil and the primary coil (particularly the lateral distance) should reach or fall short of a predefined threshold value. By way of example, the distance may be the geometrical distance between one or more predefined points on the primary coil and one or more predefined points on the secondary coil.
The vehicle includes at least one camera that is set up to capture surroundings of the vehicle. By way of example, the at least one camera may be a front camera that is set up to capture surroundings in front of the vehicle, and/or a rear camera that is set up to capture surroundings behind the vehicle. In particular, the at least one camera can capture surroundings in the direction of travel of the vehicle (e.g. a front camera for forward motion and/or a reversing camera for backward motion). It is also possible to use a multiplicity of cameras in order to capture the surroundings of the vehicle. Furthermore, the vehicle can also include further ambient sensors, such as ultrasonic sensors, which can be used to ascertain a distance to particular objects (e.g. to predefined reference objects) in the surroundings of the vehicle.
The control unit is set up to receive image data from the at least one camera of the vehicle. By way of example, the image data may be an image of the surroundings of the vehicle, which are captured by the camera, at a particular instant and/or may be a sequence of images at a sequence of instants.
Furthermore, the control unit is set up to access reference data. The reference data can include information about at least one predefined reference object in the captured surroundings of the vehicle. By way of example, the reference data can be information about one or more visual features of the at least one reference object that are able to be detected in the image data from the camera. In particular, the reference data can include a graphical reproduction of the at least one reference object, the graphical reproduction being able to be compared with the image data in order to detect the at least one reference object in the image data. Furthermore, the reference data can include information about a physical size of the at least one reference object. The physical size in the reference data can be compared with the size of the at least one detected reference object in the image data in order to ascertain a distance of the camera (and the vehicle) from the at least one reference object.
Furthermore, the reference data can include information about the position of the at least one predefined reference object relative to the primary coil. In particular, the reference data can include information concerning spatial coordinates of the at least one reference object in a predefined coordinate system. In addition, the reference data can include information concerning spatial coordinates of the primary coil in the predefined coordinate system. The respective coordinates then represent the relative position between reference object and primary coil.
The control unit may additionally be set up to take the reference data as a basis for detecting the at least one predefined reference object in the received image data. As set out above, the control unit may be set up particularly to detect a graphical reproduction of the reference object in the image data. Furthermore, the control unit may be set up to take the detected at least one reference object as a basis for ascertaining a position of the secondary coil relative to the primary coil. A position of the detected reference object in the image data can provide information about the position of the vehicle relative to the reference object. In addition, a detected size of the reference object can provide information about the distance between the vehicle and reference object.
In particular, the control unit may be set up to take the detected at least one reference object as a basis for ascertaining a camera angle for a ray between the at least one camera and the at least one reference object. The camera angle indicates the angle at which the vehicle is oriented relative to the at least one reference object. The control unit may be set up to take the ascertained camera angle as a basis for ascertaining a distance of the secondary coil to the at least one reference object. This can involve the use of particularly triangulation methods and/or other trigonometric methods (e.g. application of the triangle rule for simultaneous detection of at least two reference objects in the image data).
The control unit may additionally be set up to receive information concerning a steering turn and concerning a wheel speed of the vehicle. The received information concerning the steering turn and concerning the wheel speed can be taken as a basis for ascertaining a motion of the vehicle. The information concerning the steering turn and the wheel speed can be synchronized to the information obtained from the image data (e.g. to the ascertained camera angle). This can then be used to ascertain a motion (and/or position) of the vehicle relative to the at least one reference object. This can involve the use of triangulation methods, for example.
The reference data can include information about a multiplicity of predefined reference objects. The multiplicity of predefined reference objects may be arranged along an approach trajectory of the vehicle with respect to the primary coil. Thus, the multiplicity of predefined reference objects can assist the entire positioning process for the vehicle. The control unit may be set up to receive a time sequence of image data (particularly a time sequence of images) from the at least one camera of the vehicle along the approach trajectory. In addition, the control unit may be set up to detect the multiplicity of predefined reference objects in the time sequence of image data. The individual reference objects may be detectable on various image data (particularly images or frames) for the sequence of image data. By way of example, this can ensure that at least one predefined reference object can be captured by the at least one camera of the vehicle at every instant in the positioning process. Thus, the positioning process for the vehicle can be assisted continuously. In addition, the control unit may be set up to bypass one or more instants of the positioning process at which a predefined reference object cannot be captured. This can involve the use of vehicle-internal data (such as the steering turn and/or the wheel rotation) in order to ascertain the motion of the vehicle.
The control unit may be set up to receive the reference data from a pilot unit of the primary coil. The reference data can be transmitted via a wireless communication network, for example (e.g. WLAN). This allows the vehicle to approach an unknown charging station, and to be provided with the reference data that are required for the positioning process at the beginning of the positioning operation. The reference data can be stored in a memory unit of the vehicle. The control unit may additionally be set up to use the stored reference data when the same charging station is approached repeatedly. In addition, further data (e.g. an already ascertained intended trajectory of the vehicle) can be used and if need be updated. This allows the positioning operation to be improved when a charging station is approached repeatedly.
The control unit may be set up to prompt a control signal to be sent to the pilot unit of the primary coil in order to illuminate the at least one predefined reference object. The control signal can be transmitted via the abovementioned wireless communication network. Transmission of the control signal ensures that the at least one camera of the vehicle can capture the at least one predefined reference object reliably.
The control unit may be set up to provide information concerning the position of the secondary coil relative to the primary coil for positioning of the secondary coil relative to the primary coil. By way of example, the information concerning the position of the primary coil can be displayed on a screen of the vehicle, and in this way can assist a driver of the vehicle in positioning the vehicle. Alternatively or additionally, the information concerning the position of the primary coil can be provided for a parking assistance function of the vehicle. The control unit may then be set up to prompt the parking assistance function of the vehicle to move the vehicle such that the distance between the secondary coil and the ascertained position of the primary coil reaches or falls below the predefined threshold value (in order to achieve sufficiently great magnetic coupling).
Overall, the use of at least one camera of the vehicle allows precise positioning of the vehicle over a primary coil. The at least one camera of the vehicle is typically already installed for other driver assistance systems (e.g. parking aid) in the vehicle, which means that the use of the at least one camera of the vehicle allows an inexpensive solution for the positioning of the vehicle.
The control unit may be set up to generate a graphical representation of the surroundings of the vehicle with the ascertained position of the primary coil. In this case, it is preferred for the primary coil to be graphically highlighted in the graphical representation in comparison with the surroundings of the vehicle, so that the primary coil is clearly identifiable (e.g. by virtue of highlighted contours). Furthermore, the control unit may be set up to prompt the graphical representation to be output on a screen of the vehicle (e.g. on a central display, e.g. on the center console, of the vehicle).
The graphical representation can comprise a “top view” view of the vehicle and of the surroundings of the vehicle with (a highlighted image of) the primary coil. Furthermore, the graphical representation can include a symbolic representation of the secondary coil in the vehicle. This allows a driver to see the position of the secondary coil and the position of the primary coil simultaneously. This assists the driver in reducing the distance between the secondary coil and the primary coil. Alternatively or additionally, the graphical representation can include a “rear view” view of the vehicle (from a rear camera) or a “front view” view of the vehicle (from a front camera). In particular, images can be combined in an artificial aperture. This makes it possible to take account of images from different cameras with a different angle of vision/position and/or images from one camera over time. This multiplicity of images can be synthesized to produce a new image, the new image showing the surroundings of the vehicle with the detected primary coil from a new angle of vision.
The control unit may be set up to highlight the symbolic representation of the secondary coil separately when the distance between the secondary coil and the primary coil reaches or falls below the predefined threshold value. This makes it possible to display to the driver that the vehicle is positioned such that there is sufficient magnetic coupling between primary coil and secondary coil.
The control unit may be set up to ascertain an intended trajectory for the vehicle that allows the distance between the secondary coil and the primary coil to be reduced such that the distance reaches or falls below the predefined threshold value. Furthermore, the control unit may be set up to take the received information concerning the steering turn as a basis for ascertaining an actual trajectory of the vehicle. A graphical representation of the intended trajectory and the actual trajectory can be output on the screen of the vehicle (e.g. together with the graphical representation of the surroundings of the vehicle). This displays to the driver of the vehicle how he can position the vehicle correctly over the primary coil.
According to a further aspect, a vehicle (particularly a two-track vehicle, e.g. a motor car) is described. The vehicle includes a secondary coil for picking up electric power from a vehicle-external primary coil. Furthermore, the vehicle includes at least one camera that is set up to capture surroundings of the vehicle. In addition, the vehicle includes the control unit described in this document, which control unit is set up to use image data and predefined reference data to assist the positioning process for the secondary coil over the primary coil.
The vehicle can have a memory unit that is set up to store the reference data. Furthermore, the vehicle can have an onboard computer (e.g. as part of an information and communication system of the vehicle) that allows a user to input the reference data. In particular, the onboard computer can include an application for defining reference data that is described in this document. This allows a user of a vehicle to define the reference data (particularly the reference objects) for positioning the vehicle flexibly.
According to a further aspect, a method for assisting in positioning a secondary coil of a vehicle relative to a vehicle-external primary coil is described. The method includes reception of image data from at least one camera of the vehicle, the at least one camera being set up to capture surroundings of the vehicle. Furthermore, the method includes reception or provision of reference data. The reference data can be information about at least one predefined reference object in the captured surroundings of the vehicle. In addition, the reference data can include information about a position of the at least one predefined reference object relative to the primary coil. Moreover, the method includes detection of the at least one predefined reference object in the received image data, on the basis of the reference data. A position of the secondary coil relative to the primary coil can be ascertained on the basis of the detected at least one reference object.
As already explained, the reference data can be information about a multiplicity of predefined reference objects. In particular, the reference data can include information about the relative position of a multiplicity of reference objects. The method can additionally include detection of the multiplicity of predefined reference objects in the received image data. In particular, the actual relative position of the multiplicity of reference objects can be ascertained from the image data. The method can additionally include comparison of the reference data with the detected multiplicity of predefined reference objects. In particular, the information about the relative position of a multiplicity of reference objects can be compared with the actual relative position of the multiplicity of reference objects. From this, it is possible to check the consistency and/or completeness of the information concerning the reference objects. In particular, it is possible to ascertain therefrom an indicator about the reliability of the positioning of the vehicle over the primary coil as performed on the basis of the predefined reference objects.
According to a further aspect, a software (SW) program is described. The SW program can be set up to be executed on a processor and thereby to execute the method described in this document.
According to a further aspect, a storage medium is described. The storage medium can include an SW program that is set up to be executed on a processor and thereby to execute the method described in this document.
It should be noted that the methods, apparatuses and systems described in this document can be used either alone or in combination with other methods, apparatuses and systems described in this document. Furthermore, any aspects of the methods, apparatus and systems described in this document can be combined with one another in a wide variety of ways. In particular, the features of the claims can be combined with one another in a wide variety of ways.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.